The present invention relates to improvement of implants for bones. More particularly, it relates to an improved implant for a bone, a joint or a tooth root comprising a metallic base material and a coating layer of ceramics which is formed by thermally sprayed ceramic powders around the outersurface of the metallic base material.
The so-called implantology which comprises insertion of artificial materials such as artificial organs, artificial blood vessels, artificial bones and artificial tooth roots into living bodies so as to recover lost parts of living bodies or their functions has been in the limelight in recent years. It is said that a trial of implantation goes back to ancient times. Particularly in these ten-odd years, a huge number of treatments by implantation have been performed on bones and tooth roots to afford good results in the remedy of the defects or recovery of functions thereof. However, an artificial bone or tooth root which can satisfy the necessary requirements as the material for living bodies, i.e. affinity to living bodies, safety and durability, has not yet been obtained.
As metallic materials conventionally used for preparation of artificial bones or tooth roots mainly, cobalt-chromium alloys, stainless steel, titanium and tantalum are exemplified. On the other hand, as ceramic materials, aluminum oxide or carbon materials have been recently considered. Although metallic materials are excellent in mechanical strength, particularly in impact strength, they are faulty in their affinity to tissues of living bodies. For example, when a metallic implant is used, metal ions are dissolved therefrom in living bodies and produce a toxic action to bone cells around the implant. Further, the bone-formation is obstructed probably because of too large a thermal conductivity of the metallic implant. Among the metallic materials, tantalum is particularly superior in corrosion-resistance and hence has been employed as fixing plates for skulls or fractured parts of bones and implants for jawbones since around 1940. The metal is, however, difficult to process. To the contrary, ceramic materials show generally a good affinity to bones, and the bone tissues penetrate into fine pores of the ceramic materials to produce a strong fixation, without reaction between the ceramic material and the tissue. Besides, they are also excellent in durability, that is, they are resistant to corrosion decomposition. But on the other hand, they possess a poor impact strength.
As the results of the present inventors' studies, it has now been found that a desirable implant for bones, joints and tooth roots having a sufficient impact strength and hence an excellent break-resistance while retaining the advantages of ceramic materials above-mentioned can be obtained by coating a metallic base material with ceramic powders.
Accordingly, an object of the present invention is to provide an improved implant for a bone, a joint and a tooth having excellent mechanical strength and affinity to living bodies.
Another object of the present invention is to provide a method for improving metallic implants by thermally spraying ceramic powders on the surface of the metallic base material to form a layer of the ceramics.
A further object of the present invention is to provide an improved artificial bones useful as implants for various bones including joints and tooth roots with good durability.
A still further object of the present invention is to provide a method for producing the improved implants.
The implant of the present invention comprises a metallic base material and a coating layer of ceramics which is formed by thermally spraying ceramic powders around the outersurface of the metallic base material.